The Periodic Table
Understand how elements are organized and what information the table provides.
Learn
Reading the Periodic Table
- Atomic number: Number of protons in an atom
- Atomic mass: Average mass of an element's atoms
- Chemical symbol: One or two letter abbreviation (H, He, Na)
- Groups (columns): Elements with similar properties
- Periods (rows): Elements with same number of energy levels
- Metals, Nonmetals, Metalloids: Three main categories
Practice
Question 1: What does the atomic number tell you about an element?
Answer
The atomic number tells you the number of protons in the nucleus of an atom.
Question 2: Carbon has atomic number 6. How many protons does a carbon atom have?
Answer
A carbon atom has 6 protons.
Question 3: What are groups on the periodic table?
Answer
Groups are vertical columns. Elements in the same group have similar chemical properties.
Question 4: What are periods on the periodic table?
Answer
Periods are horizontal rows. Elements in the same period have the same number of electron energy levels.
Question 5: Where are metals typically found on the periodic table?
Answer
Metals are found on the left side and center of the periodic table.
Question 6: What is the chemical symbol for gold?
Answer
Au (from the Latin word "aurum").
Question 7: The element sodium has symbol Na and atomic number 11. How many protons and electrons does a neutral sodium atom have?
Answer
11 protons and 11 electrons (neutral atoms have equal protons and electrons).
Question 8: What is a metalloid?
Answer
A metalloid has properties of both metals and nonmetals. Examples include silicon and boron.
Question 9: Elements in Group 18 are called noble gases. Why are they considered unreactive?
Answer
Noble gases have full outer electron shells, making them stable and unreactive.
Question 10: Oxygen has atomic mass of about 16 and atomic number 8. What do these numbers tell you?
Answer
Atomic number 8 means 8 protons. Atomic mass 16 means the average mass of oxygen atoms is about 16 atomic mass units (protons + neutrons).